This invention relates to chipper apparatus, and more particularly, to chipper apparatus which includes a rotating chipper disc and one or more knives mounted on this disc operable to produce wood chips on the feeding of wood material against the disc. The invention more specifically is directed to a novel construction for a double-edged chipper knife usable in such apparatus.
In recent years, so-called double-edged chipper knives have become increasingly popular, since through turning of the knife a convenient way is provided for replacing the cutting edge which is used in the chipper without having to grind an edge. Furthermore, such knives lend themselves to use in a returnable system, wherein after dulling of both edges, they are returned or thrown away with the elimination of any grinding by the user.
While the advantages of double-edged knives are recognized, certain problems have been experienced with knife constructions known to date. Certain knives, for instance, have a geometry which is somewhat complex, introducing problems in making the knife and in properly mounting it on the chipper disc. A problem of general concern is that with many knife constructions, and during use, wood particles, resins, etc. tend to build up between the knife and the structure mounting it, causing displacement of the knife in its mounting and overheating of the knife. Furthermore, any system which relies upon clamping onto certain blade surfaces in a knife introduces a problem, in that should it be desired to change the angle of these blade surfaces, such also requires a change in the clamping structure which is used to clamp onto the knife in the chipper. Another problem which has been encountered is the tendency for a knife, when such twists in its mounting during use, to bend or break the mounting structure which clamps it in place on the chipper.
A general object of this invention is to provide an improved double-edged knife for a chipper with a construction taking care of many of the difficulties discussed above.
A more specific object is to provide a double-edged chipper knife which lends itself to being securely mounted in a chipper disc, but nevertheless, is devoid of the complex geometry characterizing certain prior art knives.
Another object is to provide a double-edged chipper knife which has a back side in part surfaced by blade surfaces, and in part surfaced by a bearing surface which is the surface utilized in clamping the knife in place. With the construction contemplated, any changes in the angles of the blade surface do not affect the placement or inclination of the bearing surface.
A further feature and object of the invention is a knife which features an elongate key-receiving channel on one of its sides relied upon to anchor the knife in place on the chipper disc, and organized in such a manner as to inhibit build up of wood residues between the knife and the structure mounting it.
The double-edged knife of this invention may be constructed to have a relatively small edge-to-edge cross sectional dimensional, with the knife, nevertheless, being properly supportable in the chipper with the knife held from fluttering (which affects the uniformity of the chips produced and results in premature dulling of the knife), and with the knife supported in such a manner as not to affect its pull angle into the wood. The knife, furthermore, may be firmly held in a manner inhibiting twisting of the knife in its mounting and with forces generated in the knife during cutting properly restrained.